In apparatus for chemical analysis of a sample, the sample, in some form is frequently exposed to surfaces such as electrodes for establishing desired electric field, within the interior of a detector. The interaction of sample substance on these surfaces may create an undesired effect. These surfaces, for example, may catalyze some chemical reaction by which the chemical analysis is distorted, or these surfaces may be at an elevated temperature which promotes decomposition of sample molecules in contact therewith.
Surface-sample molecular interactions may also distort the subsequent analysis of the sample, for example by distortion of the peak shape in a chromatogram due to surface forces acting on the sample at the electrode surfaces which affect retention time within an ion trap or similar detector.
These phenomena are known in the prior art and it was known to reduce the catalytic decomposition effect by applying a specific passivating agent. U.S. Pat. No. 5,055,678 describes the use of chromium or oxidized chromium surfaces for ion trap and ionization chambers. The same reference also describes the use of organic silanizing reagents which chemically bond to specific chemical sites on the electrode surface.
It is desired to achieve a greater degree of isolation between samples and the instrumental environment for an analytical component. The present invention, a fused silica coating (as a specific embodiment) having thickness of the order of 0.02 to 0.1 micron, has been found to substantially improve peak shapes in chromatographic apparatus in comparison with chromium coated stainless steel electrodes of prior art. Fused silica has been shown to have the advantage of not only reducing chemical decomposition at the surface, but also reducing peak tailing due to physical or chemical absorption on the ion trap surfaces.